Ungrafted polymer precipitated because polymer is insoluble in ionic liquid. After the graft polymerization, polymerization was terminated by the addition of small amount of methanol. Therefore, ionic liquid contains polymer-grafted nanoparticles, unreacted monomer, ungrafted polymer, and methanol. The precipitate, containing polymer-grafted nanoparticle and ungrafted polymer, was removed by filtration.
On the other hand, filtrate contains unreacted monomer and methanol. Methanol and monomer were removed from the filtrate under high vacuum at 70°C and the resulting ionic liquid was recovered after washing with water followed by drying under high vacuum at 50°C. The ionic liquid recovered can be reused.
Therefore, the reduction of wastage of solvent by recycle and scale-up synthesis of polymer-grafted nanoparticles were achieved by the use of ionic liquid as a reaction solvent (Fig. 2.27).
Acknowledgment This study was partly supported by a Grant in Aid for Scientific Research from the Ministry of Education, Culture, Sport, Science and Technology of Japan (No. 15360357), which is gratefully acknowledged.
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